chore(deps): latest grunt-newer

The 0.6 release deprecates the "any-newer" task (which you were not using) and folds the same functionality into the "newer" task.  See the [changelog](https://github.com/tschaub/grunt-newer/blob/master/changelog.md) for more detail.  This avoids issues like tschaub/grunt-newer#31.
Merge pull request #586 from tschaub/patch-1

Update grunt-newer